digraph Memory {
  rankdir=LR;
  node [shape=box];
  M [label="Initial memory"];
  X [label="Store x = 42"];
  Y [label="Loop: Store y"];
  L [label="Load x -> 42"];
  M -> X -> L [color=blue]; M -> Y [color=green];
  X -> MemMerge [color=blue]; Y -> MemMerge [color=green];
  MemMerge -> Return; L -> Return;
}